1. Field of the Invention
The present invention relates to an endoscope which incorporates at a distal end portion thereof an observation portion such as an ultrasound observation portion.
2. Description of the Related Art
Generally, endoscopes have a rigid distal end portion at a distal end of an elongated insertion portion to be inserted into a subject or the like. Such distal end portion includes various observation portions such as an ultrasound observation portion that transmits and receives ultrasound and an optical observation portion that picks up an optical image, and the observation portions are housed in a case made of a rigid member such as metal or resin. The shape of the rigid member configuring the case or the like roughly defines the outer shape of the distal end portion of the endoscope.
Generally, corner portions at which two or more planes or curved faces and the like are aggregated exist at the distal end side of the case. For example, as illustrated in Japanese Patent Application Laid-Open Publication No. 2011-206428, in the convex-type ultrasound endoscope, the case (first support portion) configuring the distal end portion includes side faces located respectively on both sides of the acoustic lens portion of the ultrasound transducer, a face (bottom face) opposed to the rear face side of the acoustic lens portion, and end face which is continuously formed at the distal end side of these side faces and the bottom face, and corner portions are formed respectively at the aggregation portions of these faces.
Among the corner portions formed in the case, the corner portions formed between the end face and other faces are likely to interfere with the body wall or the like and to be an insertion resistance when inserting the endoscope into the narrow bronchus and the like. Therefore, in order to reduce such an insertion resistance, the corner portions of the case configuring the distal end portion are generally subjected to a predetermined rounding processing and the like.